Traditional surgery methods involve incisions that allow a surgeon direct access to the part of the body that is to be operated upon. While this can offer the benefit of direct visual and/or tactile feedback to the surgeon, the procedure can be relatively evasive. For instance, correction of abnormalities of the heart is accomplished by cutting through bones and muscle of the chest. This leads to a long and painful recovery that stems as much or more from the side effects of the opening the chest as from the work on the heart itself.
A set of relatively new techniques have shown significant promise in alleviating much of the trauma often associated with traditional surgery methods. These techniques involve small incisions and are often referred to as Minimally Invasive Surgery (MIS). Using specialized techniques surgeons perform surgery through the small incisions. For example, specially designed probes (e.g., catheters) can be introduced to the heart by feeding the probe through a vein. The surgeon manipulates the probe near a desired location to perform the necessary action, such as ablation of abnormal tissue.
An important component of MIS is the ability of the surgeon to properly maneuver the probes to the desired locations. The surgeon cannot directly see the inserted probe and its position within the patient. Thus, a number of different imaging modalities can be used to guide placement of the probe. Competing with the desire for accurate guidance is the desire for small probe size, fast procedures, simplicity and reduced costs. One method that has gained relatively wide acceptance is an electroanatomic mapping system (EMS). An EMS uses one or more electrical probes for which three-dimensional positioning information can be determined relative to a reference point, such as a reference patch placed external to the patient. The positioning information is then correlated to the internal structure of the patient. While this procedure has seen a wide degree of success, a number of problems and difficulties hamper the true potential of these and related procedures.